Physics
Radiocarbon is produced in the atmosphere as a result of

Lightning discharge in atmosphere.
Collision between fast neutrons and nitrogen nuclei present in the atmosphere.
Action of ultraviolet light from the sun on atmospheric oxygen.
Action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere.

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Physics
Skating on ice is possible because

The pressure on the ice due to skate raises its melting point
Ice is cold
The surface of ice is smooth
The pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water

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